Faster than mallard?

[crtty]

I found a paragraph about steam engines.It said an American engine called "big machine" have made a speed record faster than mallard:226km/h
Does anyone konw what the type of this "big Machine"is?
P.s:this is the original paragraph(in Chinese)
" 1829年，“火箭号”蒸汽机车在英国的利物浦至曼彻斯特铁路线上，创造出了时速57公里的当时地面行驶车辆的最高速度；1855年，一辆夏普和罗伯尔机车把蒸汽机车的最高时速提高到100公里；1890年，在法国蒙特罗又以每小时114公里的速度再次打破这个世界纪录；1893年，美国一台“999”号蒸汽机车，曾创下当时每小时181公里的火车行驶速度新纪录；1905年宾夕法尼亚的一名列车员创造了时速220.5公里的新世界纪录；此外，德国的一台流线型七轴大型蒸汽机车于1925年在柏林至汉堡间运行的最高时速曾达到200公里；英国伦敦东北铁路公司“野鸭号”蒸汽机车于1938年7月3日在林肯郡葛兰山至诺山郭郡彼得市铁路上运行的最高时速达到202.8公里；美国的“大机器号”蒸汽机车于1946年为了弥补一次误点，曾把速度开到每小时226公里。这些蒸汽机车，不仅在当时、就是与当今的先进机车相比也不逊色。 "

[Gumboots]

Haven't heard of it before, and the text you quoted doesn't give much detail. According to Google Translate it says:

America's "big machine number" steam locomotive in 1946 In order to compensate for time delays, once open to 226 km per hour speed.

It's plausible, although as far as I know it's not confirmed. For example, some of the later Hudsons were capable of very high speeds and are claimed to have regularly hit 120 mph (193 km/h) on level track. I suppose that with a light load and a good driver, in perfect conditions, possibly on a downhill grade, one of them may have briefly reached 226 km/h. The N&W J class was also known for being able to go as fast as the driver's courage would allow, but I don't know what their regular service speed was.

[sbaros]

I've read somewhere about this case several decades ago, I think it was an alarmed travelling federal railroad inspector that timed a delayed Pennsy streamliner (I think some kind of Duplex) between mileposts in 1946 and was horrified to calculate these 226 km/h. I cannot recall the source.

[Akarin]

I believe they are talking about the Pennsylvania Railroad T1 4-4-4-4. Rumor has it that the T1 exceeded the Mallard, but there was never an official recording of that speed. All the T1's were scrapped however as it turns out some people have decided to build a new one https://prrt1steamlocomotivetrust.org/